Zn diffusion technology for InP-InGaAs avalanche photodiodes

This paper presents a study of Zn diffusion process into InP and InGaAs/InP epitaxial heterostructures grown by molecular beam epitaxy. It was found that both diffusion systems: a resistively heated quartz reactor with a solid-state Zn vapor source placed inside and hydrogen or nitrogen as the carrier gas and MOCVD reactor with hydrogen as the carrier gas allow achieving similar dopant concentration above 2*10e18 cm-3. The depth of the diffusion front in the InP layer is located from 2 to 3.5 μm depending on the temperature and time of the diffusion process. The diffusion of Zn into InP through the intermediate InGaAs layer provides better surface quality comparing with direct zinc diffusion into InP surface.

МОДЕЛИРОВАНИЕ ВЗАИМОДИФФУЗИИ И ФАЗООБРАЗОВАНИЯ В ТОНКОПЛЕНОЧНОЙ ДВУХСЛОЙНОЙ СИСТЕМЕ ПОЛИКРИСТАЛЛИЧЕСКИХ ОКСИДОВ ТИТАНА И КОБАЛЬТА

Предложена модель, развивающая теорию Даркена взаимной диффузии в бинарной системе с неограниченной растворимостью, на случай реакционной взаимодиффузии в двухслойной системе, состоящей из поликристаллических фаз оксидов двух металлов и содержащей подвижные и неподвижные компоненты в каждой из фаз. В рамках модели проведён численный анализ экспериментальных концентрационных распределений титана и кобальта в тонкоплёночной системе TiO2-x–Co1-yO, полученных методом резерфордовского обратного рассеяния, при отжиге в вакууме. Анализ выявил доминирующую роль диффузии подвижного кобальта в фазу TiO2-x по сравнению с диффузией подвижного титана в фазу Co1-yO и область локализации образования фаз сложных окси-дов в окрестности межфазной границы TiO2-x–Co1-yO. REFERENCES Chebotin V. N. Fizicheskaya khimiya tverdogo tela [Physical chemistry of a solid body]. M.: Khimiya Publ., 1982, 320 p. (in Russ.) Tretyakov Yu. D. Tverdofaznye reaktsii [Solid phase reactions]. M.: Khimiya Publ., 1978, 360 p. (in Russ.) Afonin N. N., Logacheva V. A. Interdiffusion and phase formation in the Fe–TiO2 thin-fi lm system. Semiconductors, 2017, v. 51(10), pp. 1300–1305. https://doi.org/10.1134/S1063782617100025 Afonin N. N., Logacheva V. A. Cobalt modifi cation of thin rutile fi lms magnetron-sputtered in vacuum technical. Technical Physics, 2018, v. 63(4), pp. 605–611. https://doi.org/10.1134/S1063784218040023 Kofstad P. Nonstoichiometry, diffusion, and electrical conductivity in binary metal oxides. Wiley-Interscience, 1972, 382 p. Smigelskas A. D., Kirkendall E. O. Zinc Diffusion in alpha brass. Trans. AIME, 1947, v. 171, pp. 130–142. Chambers S. A., Thevuthasan S., Farrow R. F. C., Marks R. F., Thiele J. U., Folks L., Samant M. G., Kellock A. J., Ruzycki N., Ederer D. L., Diebold U. Epita xial growth and properties of ferromagnetic co-doped TiO2 anatase. Appl. Phys. Lett., 2001, v. 79, pp. 3467–3469. https://doi.org/10.1063/1.1420434 Matsumoto Y., Murakami M., Shono T., Hasegawa T., Fukumura T., Kawasaki M., Ahmet P., Chikyow T., Koshihara S., Koinumaet H. Room-temperature ferromagnetism in transparent transition metal-doped titanium dioxide. Science, 2001, v. 291, pp. 854–856. https://doi.org/10.1126/science.1056186 Darken L. S. Diffusion, mobility and their interrelation through free energy in binary metallic systems. Trans. AMIE, 1948, v. 175, pp. 184–190. Samarsky A. A. [Theory of difference schemes]. M.: Nauka Publ., 1977, 656 с. (in Russ.) Afonin N. N., Logacheva V. A., Gerasimenko Yu. A., Dolgopolova E. A., Khoviv A. M. Interaction of cobalt and titanium with thin fi lms of their oxides during vacuum annealing // [Condensed Matter and Interphase], 2013, v. 15 (3), p. 232-237. URL: https://journals.vsu.ru/kcmf/article/view/902/984 (in Russ.)

Zinc Diffusion and Availability Affected by Different Sources in Soils of Contrasting Textures

Trends in new fertilizer technologies should balance the nutrient release rate from fertilizers with plant demands over time, while developing suitable physical characteristics of the fertilizer’s particles. The objective of this study was to evaluate the performance of three zinc fertilizers [ZnO, ZnSO4, and a commercial co-granulated ZnO+S0 fertilizer (ES_Zn)] on Zn diffusion in soil and their agronomic performances. A Petri dish trial was carried out in order to evaluate the diffusion of Zn in the soil. The experiment was designed as a factorial scheme (3 + 1) × 2 × 3, with three Zn sources, one control treatment (without Zn application), two soils of contrasting textures (sandy and clay), and three incubation times (1, 30 and 60 d). The experiment was carried out under a completely randomized design with four replications. Zinc diffusion was assessed according to the method proposed by Degryse et al. (2015) along of incubation times. For that, a ZnSO4 solution or ZnO suspension was applied by pipetting 15 μL of solution or suspension into a small hole (~0.5-cm deep) in the center of the Petri dish. A single pastille of ES_Zn fertilizer (30±0.5 mg) was placed in the center of the Petri dish, at the same depth. Soil was watered to 80% of field capacity. Filter papers (Whatman) were impregnated with CaCO3 and placed on the soil surface. After 2 h of reaction, the CaCO3-impregnated filter papers were collected, and the precipitated Zn in the papers was colored with dithizone, giving a pink color. The performance of Zn sources was evaluated in a greenhouse through a successive maize-soybean-millet crop. The trial was designed as a 2 × (3 × 3 +1) factorial scheme, being two soils (sandy and clay), three Zn sources (ZnSO4, ZnO, and ES_Zn), three Zn doses (1.5, 3.0, and 6.0 mg dm-3 Zn), and a control treatment. The experiment was a randomized block design with four replications, being the experimental unit composed of a pot with 4 dm3 of soil. Pastille ES_Zn, ZnO (as suspension), and ZnSO4 (as solution) were applied at five equidistant points, at 5 cm below the soil surface. After 30, 60 and 60 days of planting, shoot of maize soybean and millet were harvest, oven-dried at 70 °C for 72 h (until constant weight), weighed and milled for chemical analysis. ES_Zn fertilizer promoted a delay Zn release in the soil, being effective as a fertilizer only in the last crop (millet), as well as ZnO. Zinc oxide and ZnSO4 had similar performances for increasing Zn availability in the inner soil portion, but its diffusion in soil was superior when the source was sulfate. The highly soluble ZnSO4 was more effective than ZnO-based fertilizers in terms of plant nutrition, especially for the two first crops. Our results also suggest that ZnO is solubilized in soil at high pH (6.6), its dispersion in soil being a key factor for the dissolution rate.

Zinc diffusion induced precipitation of σ-phase in austenitic stainless steel

Zinc diffusion-induced degradation of AISI 316LN austenitic stainless steel pot equipment used in 55%Al-Zn and Zn-Al-Mg coating metal baths is described. SEM/EDS analyses results showed that the diffused zinc reacts with nickel from the austenite matrix and results in the formation of Ni-Zn intermetallic compounds. The Ni-Zn intermetallic phase and the nickel depleted zones form a periodic and alternating layered structure and a mechanism for its formation is proposed. The role of cavities and interconnected porosity in zinc vapour diffusion-induced degradation and formation of Ni-Zn intermediate phases is also discussed. The formation of Ni-Zn intermediate phases and the depletion of nickel in the austenite matrix results in the precipitation of σ-phase and α-ferrite in the nickel depleted regions of the matrix. This reaction will lead to increased susceptibility to intergranular cracking and accelerated corrosion of immersed pot equipment in the coating bath. Zinc diffusion induced precipitation of σ-phase in austenitic stainless steels that we are reporting in this work is a new insight with important implications for the performance of austenitic stainless steels in zinc containing metal coating baths and other process industries. This new insight will further lead to improved understanding of the role of substitutional diffusion and the redistribution of alloying elements in the precipitation of σ-phase in austenitic stainless steels.